Experimental study of saturated pool boiling from downward facing structured surfaces

Saturated pool boiling from downward facing and structured surfaces were measured in saturated deionized water to study the effects of inclination angle and structures on boiling heat transfer coefficients and critical heat flux (CHF). The inclination angles were 5°, 30°, 45°, 60° and 90° (vertical), two structured surfaces with interconnected-grooves and cavities were investigated. The results indicated that the CHF increases with the increased inclination angle. Compared with the plain surface, 61–91% higher CHF increase was achieved on the interconnected-grooves surface with quadrilateral array cavities, and more than 102% CHF increase was obtained on the interconnected-grooves surface with triangular array cavities. The structured surfaces can form a liquid–vapor conversion system which consists of cavities as stable cavity-centric vaporization cores and interconnected grooves as the cooling water supply pathways, which results in significant heat transfer enhancement and CHF increase. Phenomenological characteristics regarding the bubble dynamic on the structured surfaces were illustrated at different heat fluxes. •Two structured surfaces were designed to enhance the downward facing boiling.•The CHF on the structured surfaces and the orientation effect were investigated.•The results of structured surfaces show significant CHF enhancement.•The bubble dynamics and the mechanism of CHF enhancement were analyzed.